A horizontal band saw machine has a configuration in which a saw blade housing is provided on a base frame having vise device that can fixedly hold a work so as to be vertically movable, the saw blade housing has a driving wheel and driven wheel that are rotatably provided separately from each other in the horizontal direction and an endless band saw blade is wound around the driving wheel and the driven wheel. When the saw blade housing lowers from the risen position, the band saw blade cuts the work.
According to a first background art, in a conventional horizontal band saw machine, upper and lower straight saw blade traveling parts are formed between the driving wheel and the driven wheel and generally, the lower traveling part of the band saw blade cuts the work. With this configuration, there is a problem that the vertical dimension of the whole horizontal band saw machine becomes larger.
Thus, the configuration in which the upper traveling part of the band saw blade cuts the work is also proposed (for example, U.S. Pat. Nos. 5,062,335, 3,182,538 and 2,898,669).
With the configuration described in two of the U.S. Patent publications, the driving wheel and the driven wheel are rotatably provided at the front side of the saw blade housing vertically supported by a pair of guide posts so as to separate from each other in the horizontal direction and the endless band saw blade is hung around the driving wheel and the driven wheel.
When tension is applied to the band saw blade, the saw blade housing receives the tension through the driving wheel and the driven wheel. Accordingly, when a large tension is applied to the band saw blade, the stiffness of the saw blade housing needs to be improved and thus, the whole configuration becomes larger.
Furthermore, since the saw blade housing is supported being protruded forwards from the guide posts and the driving wheel and the driven wheel are rotatably supported in front of the saw blade housing, the protruded amount of the wheel from the guide posts is large and thus, vibration is easy to occur when the band saw blade cuts the work. Moreover, the dimension in the cross direction becomes larger, thereby making miniaturization difficult.
Next, according to a second background art, some conventional band saw machine have an automatic band saw blade exchange device. However, the band saw blade in the horizontal band saw machine is generally exchanged by the operator's hand. The manual exchange operation by the operator is carried out according to the following method.
An upper traveling part of the band saw blade is fixedly inserted into a saw blade insert of the saw blade guide and the remaining part of the band saw blade is attached to the driving wheel and the driven wheel. When the band saw blade is removed, the above-mentioned procedure is performed in the reverse order.
The above-mentioned conventional method for attaching the band saw blade has the following problems. That is, when the part other than the upper traveling part is attached to the driving wheel and the driven wheel, the direction is not stable due to small stiffness of the circular band saw blade and thus, it is difficult to attach the part to the driving wheel and the driven wheel. Furthermore, since the direction of the band saw blade is not stable, the edge of the band saw blade contacts against the band saw machine main unit, thereby causing damage of the edge or the main unit.
Next, according to a third background art, in the conventional band saw machine, the endless band saw blade is wound around the driving wheel and the driven wheel and the work cramped by the vise device is cut with the band saw blade of which driving wheel is rotationally driven by an electric saw blade motor and rotationally travels. The saw machine is provided with a fixed insert for guiding the band saw blade and a moving insert that moves relative to the fixed insert in response to a cut width of the work to guide the band saw blade.
An output shaft of a speed reducer is directly attached to the center of the driving wheel for rotationally driving the band saw blade. An input shaft of the speed reducer includes two types of one in which power of the electric saw blade motor is transmitted by a coupling and one in which the power is transmitted by a pulley belt (refer to Patent document 1, for example). In the other type of the saw machine, a plurality of wheels around which the endless band saw blade is wound are each driven by the saw blade motor (Japanese Patent No. 2725782).
The conventional saw machine is devised so as to efficiently transmit torque of the saw blade motor to the band saw blade and however, is not devised so as to reduce impact force of saw blade cutting resistance generated during cutting. For this reason, when a large impact force is applied to the band saw blade, this contributes to damage of the band saw blade as well as vibration and noise.
To solve the above-mentioned problem, a first object of the present invention is to provide a band saw machine in which protruded amount of the wheels from the guide posts is small, vibration generated when the work is cut with the band saw blade can be suppressed and the dimension in the cross direction can be reduced, thereby enabling miniaturization.
A second object of the present invention is to provide a band saw blade attaching auxiliary means in the double-post horizontal band saw machine using a circular band saw blade in which an edge of the band saw blade can be easily attached to a band saw machine main unit without touching the main unit when the operator attaches the band saw blade to the driving wheel and the driven wheel, and a band saw blade attaching method using the device.
Furthermore, the third object of the present invention is to provide a band saw machine and a saw blade driving method in which the impact force of the saw blade cutting resistance generated during cutting can be reduced, damage of the band saw blade can be prevented and vibration and noise can be reduced.